1. Field of the Invention
The present invention relates to a DC power module. More specifically, this invention relates to a DC power module composed of a DC voltage source and supercapacitors in parallel connection for driving miscellaneous multi-functional tools with interchangeable attachments or accessories for various tasks.
2. Description of the Related Art
In daily living, there are numerous works requiring an overpowering yet brief pulse of force or energy to complete. For example, operations such as to drive nails into wood, to drill holes in masonry, and to ignite the combustion engines of mowers or vehicles all depend on a peak power from a tool at the critical moment when a high torque is demanded. A method of impulse generation is taught in U.S. Pat. No. 5,699,780, issued to Bissonnette, by rapid conversion of potential energy to kinetic energy using an elongated elastomeric bladder and a fluid such as seawater. Spears are catapulted by the foregoing impulse for spearing fish under water. A projectile in the form of nails or staples can also be ejected at an impulse generated by either a DC or an AC power module, for example, the electric nailer powered by batteries as revealed in U.S. Pat. No. 6,173,877, the battery-operated electric stapler as in U.S. Pat. Nos. 4,558,391 and 5,105,329, as well as the binding apparatus of U.S. Pat. Nos. 4,986,713; 5,818,186 and 6,086,304. Generally, the DC power tools have the convenience of no cord attachment and no location limitation, that is, they may be used at places away from the city power outlets, and they do not suffer voltage fluctuations as their AC counterparts often encounter. Furthermore, the DC motor driven impact has a greater stroke than an AC powered motor because, by being directly driven instead of gear driven, a more positive torque from the motor to a striking piston is created for the DC power tools.
Instead of launching an object, the impulse energy generated by a DC power module may be converted to an impact force for carving, chiseling, chopping, clinching, clipping, compressing, crimping, crushing, embossing, piercing, punching, splicing, and striking, etc. Numerous patents and commercial products for the foregoing applications are available, for example, U.S. Pat. Nos. 4,015,671; 4,468,826; 4,579,029; 4,991,472; 6,427,559 and 6,460,627 are all related to battery-operated hand-held tools. In operation, the required forces are directly transmitted from the interaction between pistons and a resilient member (such as spring). In the third type of application, the impulse provided by a DC power module may be directly delivered as a large electric current for welding as disclosed in U.S. Pat. Nos. 4,801,780 and 6,225,596. Using batteries as power source for the welders, light maintenance or urgent repair can be performed outside the availability of city electricity.
Heavy batteries such as lead-acid (Pbxe2x80x94H2SO4), environmentally hazardous batteries such as nickel-cadmium (Nixe2x80x94Cd), or batteries with some memory-effect such as nickel-metal hydride (Ni-MH) are universally employed in the prior art of portable power tools driven by impulse energy. In order to provide sufficient impulse, the batteries are often in large sizes and in multiple numbers that makes the tools bulky and heavy. The electronic circuits for generating the required impulse are also complex making the tools expensive. Though the foregoing batteries are rechargeable, more often than not the batteries are too low in energy content to serve at the time of emergency. Then, the users have to wait several hours for charging the batteries for a work that may only take a few minutes to finish.
The present invention provides a DC power module that can be custom made to deliver the desired impulse energy using a minimal amount of batteries and supercapacitors, as well as a simple electronic architecture. Furthermore, primary cells such as alkaline batteries, may be employed for the proposed power module. Power tools using the power module of the invention are compact, light, economical, and ready-to-go at all times. Using the power module of the invention in conjunction with interchangeable attachments or accessories, multi-purpose portable hand tools driven by impulse energy can be devised for various types of works.
Based on the energy conversion, the portable tools that are driven by impulse can be divided into three categories:
1. Tools utilize the impulse and mechanical components to launch an object such as nail, staple, or pin for fastening or binding;
2. Tools utilize the impulse and mechanical components to provide an impact force for scraping, hammering, punching, embossing, chopping, chiseling, piercing, splicing or clipping; and
3. Tools utilize the impulse directly to deliver a surge of electricity or a peak current for starting engines, for welding metals, or for actuating machineries.
It is an object of this invention to devise a method for generating the required impulse energy for conveniently and economically performing the above operations of work or maintenance. Though the aforementioned works demand a wide range of power, all of the power needs can be fulfilled by a universal power module that consists of supercapacitors and batteries connected in parallel through a control circuit.
Supercapacitors, also know as ultracapacitors and electric double layer capacitors, are accumulators of a large quantity of static charge up to thousands of farads in a single container of small volume. Essentially, all of the charge stored in supercapacitors can be discharged at once leading to an immense current that is useful to drive many power tools. Since the supercapacitors are light and compact, the tools operated on the capacitors are truly portable. Furthermore, supercapacitors can be fabricated in various configurations at low cost, the capacitors therefore are a better device than the frequently used step-up converters, inductors or fly wheels for boosting the power output of batteries. Due to the extraordinarily high power density of supercapacitors, the power output of any DC voltage sources, even the low-power device such as the primary batteries, can be augmented by tens of folds by the supercapaciters. In the power module of the present invention, the batteries serve as the charging source for supercapacitors, while an electronic controller will regulate the level of power output of supercapacitors via pulse width modulation (PWM). For attaining a long service time, the batteries are arranged to always discharge at a low rate, that is, the batteries will take care all of the low-power demands, whereas the supercapacitors provide the extra power need that cannot be offered by the batteries. By releasing the batteries from providing large power outputs, the voltage drop of batteries is minimized and their use-time is prolonged.
Theoretically, in order to fully charge the supercapacitors, the batteries should possess an identical or comparable voltage as that of the capacitors. Often many batteries have to be placed in series to match the target of charging voltage. As the number of batteries is increased, the power module for the tools become bulky and expensive. The present invention imposes individual supercapacitors or supercapacitor packs in parallel connection for charging. Then, all supercapacitors are momentarily switched to series connection for discharge when an impulse is requested. By charging supercapacitors in parallel, the number and size of charging batteries may be reduced. Whereas the supercapacitors discharge through a series connection, the capacitors can impart an impulse of twice the voltage of that of the parallel configuration to the portable tools. Only a trigger and an electromeganetic relay are needed to momentarily convert the supercapacitors from parallel configuration to series formation. Not only is the electronic control architecture simple and economical, but there is virtually no energy loss at the power amplification of batteries.
For all three types of application of electric impulse, one tool body with interchangeable attachments or accessories, and the power module of the present invention, may become the required all-in-one tools. In some cases, the interchangeable attachments can be handily integrated with the tool body as described in the present invention. In other cases, the interchangeable accessories may be provided in a supplementary kit accompanying with the tool body for various works.
These and other objectives, features as well as advantages in accordance with the present invention will become apparent from the following detailed description, and from preferred embodiments with the accompanying drawings.